Automatic electronic rangefinder

Abstract

An automatic focusing system is provided to process amplitude and phase signals of image motion in an image plane. The camera includes a focusable objective lens, optical means, oscillating means, sensing means, and a servo. Light rays reflected from an object to be focused upon are received and refracted by the objective lens to the optical means which has a rear nodal point. The optical means receives and refracts the light rays to form an image of the object in an image plane. The optical means is oscillated about the rear nodal point by the oscillating means. While the optical means is being oscillated the image remains stationary in the image plane when the objective lens is focused upon the object, but is transversely displaced and oscillates in the image plane when the objective lens is not focused upon the object. The sensing means detects and processes amplitude and phase signals generated by image motion in the image plane and directs the servo to drive the objective lens into focus.

What I claim is: 
     
       1. In an automatic focusing system for use in photographic apparatus comprising: focusable objective lens means for receiving and refracting light radiation reflected from an object to be focused upon;   optical means having a rear nodal point for receiving and refracting the light radiation from the objective lens means through the rear nodal point to form an image in an image plane;   oscillating means for oscillating the optical means about the rear nodal point, whereby the image is cyclically displaced at the frequency of said oscillation means when the image is out of focus, the magnitude of said image displacement being proportional to the degree that the image is out of focus;   sensing means including at least one photocell means displaced from the central axis of the light radiation refracted from said optical means for sensing said cyclical image displacement to provide an image displacement signal having an amplitude indicative of the magnitude of said image displacement and having a phase indicative of the direction in which said objective lens means is out of focus with respect to said object;   processing means responsive to said sensing means to provide an output signal which indicates the amount and direction said objective lens means must be moved to bring the image into focus; and   servo means responsive to the output signal for moving the objective lens means to bring the image into focus.   
     
     
       2. In an automatic focusing system for use in photographic apparatus comprising: focusable objective lens means for receiving and refracting light radiation reflected from an object to be focused upon;   reflecting means for reflecting the light radiation from the objective lens means;   optical means having a rear nodal point for receiving and refracting the light radiation from the reflecting means through the rear nodal point to form an image in an image plane;   oscillating means for oscillating the optical means about the rear nodal point, whereby the image is cyclically displaced at the frequency of said oscillation means when the image is out of focus, the magnitude of said image displacement being proportional to the degree that the image is out of focus;   sensing means including at least one photocell means displaced from the central axis of the light radiation refracted from said optical means for sensing said cyclical image displacement to provide an image displacement signal having an amplitude indicative of the magnitude of said image displacement and having a phase indicative of the direction in which said objective lens means is out of focus with respect to said object;   processing means responsive to said sensing means to provide an output signal which indicates the amount and direction said objective lens means must be moved to bring the image into focus; and   servo means responsive to the output signal for moving the objective lens means to bring the image into focus.   
     
     
       3. In an automatic focusing system for use in photographic apparatus comprising: focusable objective lens means for receiving and refracting light radiation reflected from an object to be focused upon;   reflecting means for reflecting the light radiation from the objective lens means;   optical means having a rear nodal point for receiving and refracting the light radiation from the reflecting means through the rear nodal point;   transmission means for transmitting a portion of the light radiation refracted by the optical means to form an image in an image plane, the transmission means further diverting a portion of the light radiation refracted by the optical means to a viewfinder means;   oscillating means for oscillating the optical means about the rear nodal point, whereby the image is cyclically displaced at the frequency of said oscillation means when the image is out of focus, the magnitude of said image displacement being proportional to the degree that the image is out of focus;   sensing means including at least one photocell means displaced from the central axis of the light radiation refracted from said optical means for sensing said cyclical image displacement to provide an image displacement signal having an amplitude indicative of the magnitude of said image displacement and having a phase indicative of the direction in which said objective lens means is out of focus with respect to said object;   processing means responsive to said sensing means to provide an output signal which indicates the amount and direction said objective lens means must be moved to bring the image into focus; and   servo means responsive to the output signal for moving the objective lens means to bring the image into focus.   
     
     
       4. The automatic focusing system as in claim 3 wherein the oscillating means oscillates the optical means at a frequency of at least 20 cycles per second. 
     
     
       5. The automatic focusing system as in claim 3 wherein said sensing means includes two photocell means displaced from the central axis of the light radiation refracted from said optical means for sensing said cyclical image displacement so that each of said photocell means provides an image displacement signal. 
     
     
       6. The automatic focusing system as in claim 5 wherein said output signal comprises the ratio of the difference of image displacement signals of both photocell means to the sum of the image displacement signals of both photocell means, whereby said output signal is substantially independent of image intensity. 
     
     
       7. An automatic focusing system for use in photographic apparatus comprising: focusable objective lens means for receiving and refracting light radiation reflected from an object to be focused upon;   reflecting means for reflecting the light radiation from the objective lens means;   transmission means for transmitting a first collimated portion of the light radiation reflected by the reflecting means to a viewfinder means, the transmission means further diverting a second collimated portion of the light radiation reflected by the reflecting means, whereby the second portion can be used to focus said objective lens means without altering the first portion transmitted to the viewfinder means;   optical means having a rear nodal point for receiving and refracting said second collimated portion of the light radiation through the rear nodal point to form an image in an image plane;   oscillating means for oscillating the optical means about the rear nodal point, whereby the image is cyclically displaced at the frequency of said oscillation means when the image is out of focus, the magnitude of said image displacement being proportional to the degree that the image is out of focus;   sensing means including at least one photocell means displaced from the central axis of the light radiation refracted from said optical means for sensing said cyclical image displacement to provide an image displacement signal having an amplitude indicative of the magnitude of said image displacement and having a phase indicative of the direction in which said objective lens means is out of focus with respect to said object;   processing means responsive to said sensing means to provide an output signal which indicates the amount and direction said objective lens means must be moved to bring the image into focus; and   servo means responsive to an output of the sensing means for driving the objective lens means to bring the image into focus.